The present invention generally relates to an apparatus and method for forming an image, and is capable of being applied to an image forming apparatus and method, which utilize toner of a copying machine or printer having a photosensitive drum.
In an image forming apparatus and method utilizing toner, there is carried out an image forming process for electrifying minus charges on the surface of a photosensitive drum, exposing (varying the surface potential of) the photosensitive drum to laser beams based on picture signals to form a latent image, causing it to absorb minus charged toner to form a visible image, and transferring and fixing the visible image on a paper.
In such image formation, a toner (which will be hereinafter referred to as a xe2x80x9crecovered tonerxe2x80x9d) which has been already utilized in image formation, and a toner (which will be hereinafter referred to as a xe2x80x9cnew tonerxe2x80x9d) which has not yet been utilized in image formation, are mixed to be utilized. That is, the recovered toner is recycled to be used.
Conventionally, as a method for recycling a recovered toner, there is a method for conveying a recovered toner, which leaves a cleaner auger, to a developing device by means of a connecting auger, which connects the cleaner auger to the developing device, and returning the recovered toner directly into the developing device.
In the conventional method, in view of the ratio of a new toner to the recovered toner in the developing device, both of the new toner and the recovered toner are supplied if the supply of toner is required.
For example, when the amount of toner in the developing device is very small, the operation mode is changed to a forced supply mode to force to supply both of the new toner and the recovered toner.
However, an external additive is peeled from the recovered toner, and paper powder is mixed in the recovered toner. Therefore, even if the recovered toner is supplied into the developing device, the rise of the quantity of electrification is worse than that in the case of the new toner. For that reason, in some circumstances, the presence of the recovered toner causes image fogging on an image transferred on a paper.
It is an object of the present invention to prevent the bad influence of the conventional parallel supply of a new toner and a recovered toner into a developing device.
In order to accomplish the aforementioned object, according to the present invention, an image forming apparatus comprises: recovered toner housing means for temporarily storing therein a recovered toner; a connecting/conveying device for conveying the recovered toner from a cleaner part to the recovered toner housing means; recovered toner supply means for supplying the recovered toner, which is housed in the recovered toner housing means, to a developing device; new toner housing means for housing therein a new toner; new toner supply means for supplying the new toner, which is stored in the new toner housing means, to the developing means; toner concentration ratio detecting means for detecting a toner concentration ratio in the developing device; and control means for separately controlling the recovered toner supply means and the new toner supply means in accordance with the contents detected by the toner concentration ratio detecting means, to cause to change the combination of the amounts of the recovered toner and new toner to be supplied to the developing device.
In order to accomplish the aforementioned object, according to the present invention, there is provided an image forming method for causing a connecting/conveying device to convey a recovered toner from a cleaner part to recovered toner housing means to house therein the recovered toner, and causing control means to control recovered toner supply means and new toner supply means in accordance with a toner concentration ratio in a developing device, which is detected by toner concentration ratio detecting means, to supply the recovered toner, which is stored in the recovered toner housing means, and a new toner, which is stored in new toner housing means, to the developing device, wherein the control means separately controls the recovered toner supply means and the new toner supply means in accordance with the contents detected by the toner concentration ratio detecting means, to cause to change the combination of the amounts of the recovered toner and new toner to be supplied to the developing device.